Many conventional devices are available for obtaining blood samples from a patient for laboratory testing. For example, a conventional syringe and hypodermic needle are often used to draw blood from a patient. A conventional syringe, however, may not facilitate taking multiple samples, since it may require multiple percutaneous introductions into the patient. Alternatively, a single fluid sample may be obtained using the syringe which may then be injected into individual specimen tubes, but this may increase the risk of contamination and/or accidental needle sticks.
Instead, when multiple samples are needed for laboratory tests, a blood collection needle is often used. Generally, such devices include a pair of needles disposed in line axially on a central hub or housing which are provided as part of a tube-holding device. The tube-holding device is typically a hollow cylindrical body with an open end and with the hub of the blood collection needle generally attached to the other end such that one needle extends into the cylindrical body, while the other needle extends axially beyond the cylindrical body for percutaneous introduction into a patient.
Conventional vacuum specimen tubes may then be inserted into the open end of the cylindrical body. The rubber stopper of the specimen tube is punctured by the needle inside the cylindrical body, creating a continuous passage from the percutaneous needle tip to the specimen tube. Thus, after the tube-holding device has been introduced into a patient, a series of vacuum specimen tubes may be successively inserted into it to collect samples for testing.
One of the problems often encountered when such devices are used is hemolysis. When the specimen tube is inserted into the tube-holding device, the fixed vacuum of the specimen tube may draw blood quickly through the needles. The uncontrolled flow of blood caused by the force of this vacuum may cause red blood cells to shear and break down. Potassium may be released from the cells into the blood fluid, creating inaccuracies in the laboratory tests performed on the samples.
Additionally, such conventional devices may present problems in obtaining samples from patients having poor peripheral access, such as young and elderly patients whose veins are smaller or more susceptible to collapse. Vein patency, that is, whether a vein can provide a desired volume of blood for the needed samples, is often a concern, particularly when a vein is subjected to an uncontrollable vacuum or blood flow, as may occur when multiple vacuum specimen tubes are used to obtain samples.
Attempts have been made to modify these conventional blood collection devices to respond to these problems. For example, U.S. Pat. No. 5,133,362, issued to Moss, discloses a blood collection needle which uses a smaller gauge needle for introduction into the patient than is used for the specimen tubes. The device uses such smaller gauge needles to provide improved peripheral access, while also intending to slow blood flow through the needles to reduce hemolysis. This device, however, may not properly address the viscous effects of blood flow through the needles, which contributes substantially to hemolysis in the resulting blood samples.
Thus, there is a need for an apparatus for drawing blood from a patient which substantially reduces the risk of hemolysis as blood is drawn into vacuum specimen tubes.
There is also a need for an apparatus for drawing multiple blood samples for laboratory testing which minimizes contamination and thereby improves the accuracy of test results.